The goal of this work is to evaluate the therapeutic potentialities of keto- and hydroxy-analogues of essential amino acids. Previous work has established that these compounds alone or in combination with the remaining essential amino acids induce nitrogen sparing in chronic renal failure and in starvation. Improvement has also been noted in portal-systemic encephalopathy. In the proposed work, metabolism of these compounds by isolated perfused organs, their absorption by the intestine, and their effect on the growth of normal animals on defined diets will be measured. Optimal efficacy will be sought in patients with chronic renal failure, congenital hyperammonemia, and other forms of nitrogen wastage, in each of which different mixtures may be required. BIBLIOGRAPHIC REFERENCES: Batshaw, M., S. Brusilow, and M. Walser. Treatment of carbamyl phosphate synthetase deficiency with keto-analogues of essential amino acids. New Engl. J. Med. 292:1085-1090, 1975; Batshaw, M., S. Brusilow and M. Walser. Congenital hyperammonemia treated with alpha-keto analogues of essential amino acids (abstr.). Pediatric Research 9:544, 1975.